A panorama is a “wide angle view” of the scene observed from a reference point. A goal in panoramic imaging is to capture a field of view around the reference point that includes a large azimuth (ideally 360°) and has a large vertical dimension as well. Typically, a panoramic imaging system images the panoramic scene onto an image plane, where it is measured using photographic film or an electronic sensor array.
One conventional method for capturing a panoramic image uses an ultra-wide angle lens to image a wide field-of-view onto the image plane. Unfortunately, such lenses cause significant distortion of the image—particularly as the azimuth approaches 180°.
Another approach for panoramic imaging relies on capturing a series of images with a conventional camera that is panned through a range of azimuth angles. The multiple images are then combined to form a composite image. Alternatively, a camera array having fields-of-view that diverge like spokes on a wheel can be used to generate the multiple images. Image stitching issues, slow imaging speed, and its general complexity make this approach undesirable.
To overcome some of the disadvantages of these panoramic imagers, improved systems were developed wherein a convex, shaped mirror is placed slightly above or below a conventional camera. Mirrors disclosed in the prior art include spherical, parabolic, and hyperboloidal mirrors having a wide field-of-view (up to 360°). Such imaging systems compress this wide field-of-view into a planar image having a standard field-of-view that fits within the extent of a traditional image sensor (e.g., focal-plane array, film, etc.) of the conventional camera, thereby enabling a perspective view of the scene in a single snapshot. Unfortunately, the field-of-view of a conventional camera is relatively small; therefore, the high degree of compression necessary give rise to significant reduction of the angular resolution of such imaging systems, among other drawbacks.
An efficient, high-resolution panoramic imager, therefore, remains unrealized in the prior art.